The present invention includes solutions and the preparation methods necessary for the fabrication of metal oxide cross-linked polysiloxane coating films which are useful in providing heat resistance against oxidation, wear resistance, thermal insulation, and corrosion resistance of substrates.
In the past, ceramic coatings on metallic and plastic substrates have not been widely used primarily because many ceramic coatings can be applied and processed only at high temperatures (i.e., only at temperatures above 1000.degree. C.) using expensive and time-consuming methods such as chemical vapor deposition. Therefore, aluminum alloys, plastics and other materials with low melting points were not easily protected.
U.S. Pat. No. 4,584,280 to Nanao discloses a process for preparing a porous ceramic film by applying an anhydrous solution containing an organometallic compound and a multifunctional organic compound to a substrate and thermally decomposing the substrate. The organometallic compound may be titanium alkoxide. Examples of the multifunctional organic compound include such organic compounds as glycerine, 1,4-butenediol, pentaerythritol, dextrin, arginic acid, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, carboxymethyl starch, hydroxyethyl starch, polyvinylalcohol, and mixtures thereof. The thermal decomposition is conducted at a temperature of not less than 200.degree. C., and then, if necessary, the coated substrate is baked. Nanao does not teach the formation of a polymetallicsiloxane film at low temperatures as does the present invention.
U.S. Pat. Nos. 4,455,414 and 4,347,347, to Yajima, et al. disclose an organic copolymer composed of a polycarbosilane portion and a polymetallicsiloxane portion cross-linked with each other and the process of making it. Neither patent teaches the formation of a polymetallicsiloxane film at low temperature as does the present invention.
U.S. Pat. No. 4,028,085 to Thomas discloses the combination of a hydrolyzable metal alkoxide with a partially hydrolyzed silicon tetraalkoxide to form a metallicsiloxane solution. Thomas does not teach the application of the solution to a substrate nor does it teach the heating of the solution to create a ceramic-type polymetallicsiloxane coating.
It is, therefore, an object of the present invention to provide a polymetallicsiloxane sol-gel precursor solution which can be used in the preparation of metal oxide cross-linked polysiloxane coating films which are useful in providing heat resistance against oxidation, wear resistance, thermal insulation, and corrosion resistance of substrates.
It is an object of the invention to provide a sol-gel solution, and a method of use thereof, which can be applied and processed at low temperatures (i.e., at temperatures of less than 1000.degree. C.).
A further object of the invention is to provide a polymetallicsiloxane sol-gel precursor solution which will adhere well and have an appropriate expansion coefficient, especially during temperature cycling, so that separation of the coating film from the substrate will not occur.